Engine initiative from Mercedes-Benz: New inline four and six cylinder

The biggest strategic engine initiative in the history of Mercedes-Benz will enter its decisive phase in 2017. Following the launch of the new four-cylinder diesel engine in spring 2016, next year will see the addition of no fewer than four more members to the all-new family of engines: six-cylinder in-line engines in both diesel and petrol versions, a new four-cylinder petrol engine and a new biturbo V8. At the same time, there will be world premieres for ground-breaking technologies, such as the Integrated Starter-Alternator (ISG), the 48 V electrical system and the electric auxiliary compressor (eZV). These new technologies are tuned to the vehicles on state-of-the-art test rigs at the equally new Powertrain Integration Centre (AIZ) in Sindelfingen.

„More powerful, more economical and cleaner – the new modular family of engines from Mercedes-Benz offers the right powertrain for every vehicle,“ says Prof. Dr Thomas Weber, 62, Member of the Daimler Board of Management with responsibility for Group Research at Daimler AG and Mercedes-Benz Cars Development. „The systematic optimisation of our high-tech engines plays a crucial role in the road map towards sustainable mobility. They also need to be designed with a view to all current and future requirements. A key success factor in this regard is the extensive electrification of the powertrain.“

Systematic electrification: new six-cylinder in-line petrol engine M 256
The new six-cylinder in-line petrol engine M 256 represents an outstanding example of electrification, including a 48 V electrical system. New, intelligent turbocharging, e.g. with an electric auxiliary compressor (eZV), as well as an Integrated Starter-Alternator (ISG) provide the guarantee of excellent drivability with no turbo lag. The ISG is responsible for hybrid functions, such as boost or energy recovery, while allowing fuel savings that were previously reserved for high-voltage hybrid technology. The bottom line is that the new six-cylinder in-line engine offers the same performance as an eight-cylinder machine while being much more fuel-efficient. The new petrol engine (internal code: M 256) launches next year in the new S-Class.

Systematic electrification dispenses with the need for a belt drive for ancillary components at the front of the engine, which reduces its overall length. The narrow construction, together with the physical separation of intake/exhaust, creates space for near-engine exhaust aftertreatment. The 48 V electrical system serves not only high power consumers, such as the water pump and air-conditioning compressor, but also the Integrated Starter-Alternator (ISG), which also supplies energy to the battery by means of highly efficient energy recovery.

An additional bonus is the unsurpassed refinement of the six-cylinder in-line engine. Output and torque are similar to the current eight-cylinder engine, i.e. over 300 kW (408 hp) and more than 500 Nm. In comparison with the previous V6, the CO2 emissions from the engine have been reduced by around 15 percent.

At 500 cc, the new machine has the same displacement per cylinder as the premium diesel engine family unveiled last year as well as the family of four-cylinder petrol engines.

Most powerful passenger-car diesel engine in the history of Mercedes-Benz: six-cylinder OM 656
The new top-of-the-line engine in the premium diesel family is likewise a six-cylinder in-line machine. The characteristics of the OM 656 include the stepped-bowl combustion process, two-stage exhaust turbocharging and, for the first time, the use of CAMTRONIC variable valve timing. Its design features a combination of aluminium engine block and steel pistons as well as further-improved NANOSLIDE® coating of the cylinder walls. Although there is a significant increase in output compared with the previous OM 642 (over 230 kW/313 hp instead of 190 kW/258 hp), the new engine consumes more than seven percent less fuel.

Like the already unveiled four-cylinder OM654, the new six-cylinder diesel engine OM 656 is likewise designed to comply with future emissions legislation (RDE – Real Driving Emissions). All the components of relevance for efficient emissions reduction are installed directly on the engine. The integrated technology approach of new stepped-bowl combustion process, dynamic multi-way exhaust gas recirculation and near-engine exhaust aftertreatment, combined for the first time with variable valve timing, opens the way for further reductions in consumption together with extremely low emissions. Thanks to the near-engine insulated configuration, exhaust aftertreatment has a low heat loss and extremely favourable operating conditions. This is reinforced by the CAMTRONIC switchable exhaust camshaft, which supports the consumption-neutral heating of the exhaust system.

Number of cylinders to suit the requirements: new V8 biturbo petrol engine M 176
Dynamic power delivery combined with high efficiency: the new biturbo (internal code: M 176) is one of the most economical V8 petrol engines in the world. Its special features include cylinder shutoff at part load as well as the positioning of the turbochargers in the V between the cylinder banks. From its 3982 cc displacement, the new V8 biturbo produces over 350 kW (476 hp) with a maximum torque of around 700 Nm from 2000 rpm. The new engine will consume over 10 percent less fuel than its predecessor, which is rated at 335 kW (455 hp). The new V8 will launch with this technology next year in the new S-Class.

For lower fuel consumption, when operated at part load the new M 176 shuts off four cylinders simultaneously by means of CAMTRONIC valve timing. This reduces the pumping losses while improving the overall efficiency of the remaining four cylinders by shifting the operating point towards higher loads.

Sporty specific output: new four-cylinder petrol engine M 264
A two-litre four-cylinder engine with a specific output of around 100 kW: the new Toptype petrol engine from Mercedes-Benz (internal code: M 264) advances into output regions previously reserved for high-displacement six-cylinder machines. At the same time, it consumes significantly less fuel than a comparable six-cylinder engine. The engine’s special features include twin-scroll turbochargers, belt-driven 48 V starter-alternator (BSA) and electric 48 V water pump.

The BSA is also responsible for fuel-saving hybrid functions:

Easy start: virtually imperceptible starting and acceleration of the engine

Boost in the engine-speed range up to 2500 rpm

Energy recovery up to 12.5 kW

Shifting of the load point: allows operation in a more favourable area of the engine map

Coasting with engine off

In the interests of high power output and a spontaneous engine response, Mercedes-Benz has opted for twin-scroll turbocharging. Unlike conventional systems, a twin-scroll turbocharger merges the exhaust gas ducts of cylinder pairs in the flow-optimised manifold. This turbocharging concept with systematic cylinder flow separation produces high torque in the low-rpm range together with high specific output. Further efficiency measures include intake CAMTRONIC and a friction loss reduction package.

Even cleaner: particulate filter for petrol engines as standard
Mercedes-Benz is the first manufacturer to opt for the large-scale use of particulate filters for petrol engines to further improve their environmental compatibility. After more than two years of positive experience in the field with the S 500, in 2017 further S-Class variants will be equipped with the new M 256 and M 176 petrol engines with this technology. The filter will then be gradually introduced in other new vehicle models, facelifted models and new engine generations, such as the M 264.

The particulate filter for petrol engines reduces the emissions of fine soot particles. How it works: the exhaust-gas stream is supplied to a particulate filter system. The filter has a honeycomb structure with alternately sealed inlet and outlet channels. This forces the exhaust gas to flow through a porous filter wall, which traps the soot. The filter can be continuously regenerated under corresponding driving conditions.